A number of potential gene therapy applications in the adult nervous system include neurodegenerative disorders, such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. During the last five years, lentiviral vectors have developed into extremely efficient gene transfer vehicles to the nervous system, revealing a wide range of possibilities for the treatment or such disorders. This review describes the most important and recent advances in the development of lentiviral vectors as well as the demonstration of proof-of-principle in animal models of human neurodegenerative diseases.